Piston pump device

ABSTRACT

A piston pump device has a support unit, a pump cylinder, and a pump piston arranged in the pump cylinder. The pump cylinder has a longitudinal center axis, and a cylinder bottom arranged perpendicular to the longitudinal center axis. The pump piston is movable relative to the cylinder bottom, and the pump cylinder is secured on the support unit by a securing unit. The securing unit has a leaf spring, which permits a pivoting movement of the longitudinal center axis of the pump cylinder relative to the support unit. The piston pump device is wear-resistant and runs quietly. When used as a suction pump, the piston pump device additionally permits a controllable air flow until the pump comes to a stop.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to Swiss Patent Application No.0886/10 filed Jun. 3, 2010, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a piston pump device. This pump deviceis suitable in particular as a suction pump or vacuum pump, particularlyin the medical sector. Preferred areas of use are drainage pumps foraspiration of body fluids.

BACKGROUND

Piston pumps with pump cylinder and pump piston are well known fromdifferent areas of use. For example, the applicant has for some yearsbeen selling a drainage pump with the name Dominant 35c/i, which has twodouble-action piston/cylinder systems working in opposite directions.

Other piston pumps are described in WO 95/33924 and in EP 0 791 366, forexample.

Piston pumps are exposed to forces that adversely affect their smoothrunning Various types of bearings, in particular roller bearings andsliding bearings, are used to support individual parts of the pump.However, these bearings are subject to wear. For example, slidingbearings or grooved ball bearings are always loaded on the same side.This leads to knocking noises. As a consequence, the bearings have to bereplaced after a certain length of time. Conventional grooved ballbearings also require a certain speed of rotation in order to build up alubricating film. If the pivoting speed of the pump cylinder isrelatively low, the lubricating action is unsatisfactory. This isespecially problematic in suction pumps with adjustable or controllableair flow since the pivoting speed of the cylinder also decreases whenthere is a reduction in the air flow.

SUMMARY

It is an object of the invention to make available a piston pump, inparticular for suction pumps in the medical sector, which piston pump issubject to the least possible wear and runs very smoothly.

The piston pump device according to the invention has a support unit, apump cylinder, and a pump piston arranged in the pump cylinder. The pumpcylinder has a longitudinal center axis, and a cylinder bottom arrangedperpendicular to the longitudinal center axis. The pump piston ismovable relative to this cylinder bottom, and the pump cylinder issecured on the support unit by a securing unit. According to theinvention, the securing unit has a leaf spring, which permits a pivotingmovement of the pump cylinder, or of the longitudinal center axis of thepump cylinder, relative to the support unit. The securing device can besecured on the jacket of the pump cylinder. However, it is preferablysecured on the cylinder bottom.

Leaf springs have the advantage that, with slight deflection, they arepractically free from wear. Since the pump cylinder executes onlyrelatively small pivoting movements, a small angle of deflection of theleaf spring lying within the elastic range of the spring is ensured.

The piston pump device according to the invention not only has awear-resistant bearing, it also reduces the manufacturing costs, sinceroller bearings and slide bearings can be omitted. Moreover, thereduction in the number of movable parts simplifies production and alsomaintenance and permits a compact structure.

The piston pump device can be used in particular in a suction pump. Byvirtue of the use of at least one leaf spring as a bearing, the air flowof the suction pump can be regulated or controlled until the pump comesto a stop.

The securing unit preferably forms a leaf spring clamp, wherein thisleaf spring clamp anchors the pump cylinder in relation to the supportunit, and wherein the leaf springs permit a pivoting movement of thecylinder.

A single leaf spring is preferably provided per cylinder. In theundeflected state, this leaf spring, or at least one of the leafsprings, preferably forms a plane in which a rectilinear continuation ofsaid longitudinal center axis runs.

The leaf spring has a free length and a width, wherein the leaf springis preferably made flexible in its free length. Free length is to beunderstood as the length between two opposite leaf spring clamps or leafspring bearings. The ratio of free length to width is preferably lessthan 1. A short leaf spring of this kind permits a compact structure ofthe piston pump device. The thickness of the leaf spring is preferablycirca 0.5 mm, its free length circa 13 mm, and its width circa 25 mm.

The leaf spring can be secured on the support unit and on the pumpcylinder in a variety of ways. For this purpose, in a preferredembodiment, a first cylinder-side securing element is present which isformed in one piece with the pump cylinder or is welded onto the latteror cast therein. This ensures great stability. If the cylinder-sidefirst securing element is also arranged in the cylinder bottom, thestability is increased still further.

In a preferred embodiment, the cylinder bottom has a substantially planearea for closing the pump cylinder, and an outwardly protruding securingseat which is formed integrally on this plane area and which serves toreceive the cylinder-side first securing element.

The cylinder-side first securing element can be of differentconfigurations and can be made of different materials. However, it ispreferably block-shaped, in particular cuboid, and/or made of metal.

In a preferred embodiment, the securing unit has a cylinder-sideclamping device and a support-side clamping device. The leaf spring hasa first end and a second end, wherein the first end is clamped in thecylinder-side clamping device and the second end is clamped in thesupport-side clamping device. The cylinder-side clamping device and thesupport-side clamping device each have two securing elements betweenwhich the ends of the leaf spring are arranged, wherein the two elementsare in each case screwed together. This arrangement too increases thestability.

If the spring is clamped at least at one end, preferably at both ends,fatigue fractures of the leaf spring can be avoided or at leastminimized. Good results were obtained with block-shaped securingelements, in particular made of metal. The clamping is preferably doneby means of screws, in which case the use of a torque wrench isrecommended in order in turn to minimize the risk of fatigue fracturesand material damage. It is also ensured that the connection does notcome loose or move as a result of vibrations.

The cylinder is preferably made of polyphthalamide (PPA) orcarbon-fiber-reinforced PPA. This improves the smooth running of thedevice and prevents squeaking The piston is also preferably made of PPA.The sealing ring of the piston is preferably made ofpolytetrafluoroethylene (PTFE) with carbon fibers and/or glass fibersand minerals. This leads to lubrication obtained by the first rubbing ofthe piston seal against the cylinder wall, made of the abovementionedmaterials, and in turn improves the smooth running of the device.

The piston pump device according to the invention can consist of asingle cylinder/piston combination or can be assembled from several suchcombinations, in particular two, three, four or five such combinations.The arrangement according to the invention is suitable in particular fora reciprocating cylinder/piston pair oriented parallel to each otherwith two double-action cylinders and two pistons, wherein each cylinderis secured with its own securing unit and its own leaf spring on thesupport unit.

If a suction pump according to the invention, having a cylinder/pistonpair of this kind, is provided with a single-stage gear mechanismbetween motor and crankshaft, the manufacturing costs can be reduced andthe maintenance of the pump simplified. Moreover, the pump can be madein a compact and space-saving form. These advantages are furtheroptimized if a toothed belt between crankshaft and motor is simply usedas the gear mechanism. The toothed belt also permits operation of thepump with the least possible noise.

The two piston rods of the pistons preferably work at a 90° offset tothe crankshaft.

The speed of the motor can preferably be continuously regulated. Topermit simple operation, however, an adjustment and control unit ispresent, by means of which the motor can be adjusted to at least one ortwo speeds, preferably exactly three discrete speeds. This can be donein continuously regulated motors and also in other types of motors.

The piston pump device according to the invention is suitable inparticular as a suction pump in the medical sector, particularly as adrainage pump for aspiration of body fluids or body fats.

BRIEF DESCRIPTION OF THE FIGURES

Preferred embodiments of the invention are described below withreference to the drawings, which serve only for explanatory purposes andare not to be interpreted as limiting the invention. In the drawings:

FIG. 1 shows a perspective view of a suction pump according to a firstembodiment of the invention;

FIG. 2 shows a side view of the suction pump according to FIG. 1;

FIG. 3 shows a longitudinal section through a piston pump deviceaccording to a second embodiment of the invention;

FIG. 4 shows a perspective view of a cylinder bottom with cylinder-sidesecuring part and leaf spring according to the suction pump shown inFIG. 1;

FIG. 5 shows an exploded view of the cylinder bottom according to FIG. 4with cylinder-side securing part and leaf spring, and

FIG. 6 shows a cross section through the cylinder bottom according toFIG. 4.

DETAILED DESCRIPTION

A suction pump with a piston pump device according to the invention isshown in FIGS. 1 and 2. The suction pump has an electric motor 1, whichis arranged in a motor housing 10. A support unit 2 is connected to themotor housing 10. The support unit 2 encloses a toothed belt (not shown)which on the one hand is connected to a drive shaft of the motor 1 andwhich on the other hand drives a crankshaft 6. Instead of the toothedbelt, other single-stage or multi-stage gears can also be used.

The crankshaft 6 is connected at both ends to a crank 5, 5′. Each crank5, 5′ acts on a piston rod 44, 44′. The crankshaft 6 acts at a 90°offset to the two piston rods 44, 44′. The piston rods 44, 44′ aredriven at an offset of 90° to each other.

The piston rods 44, 44′ are parts of a piston pump device. The pistonpump device has, in this example, two pump cylinders 4, 4′ and, in eachof these, a pump piston 42 which is arranged movably in the pumpcylinder 4, 4′ (see FIG. 3).

It can be seen from FIG. 3 that the piston 42 is connected to the pistonrod 44 and has a peripheral sliding seal 43. The sliding seal 43 ispreferably made of polytetrafluoroethylene (PTFE), the materialpreferably being reinforced with carbon fibers and/or with glass fibersand minerals. The cylinder is preferably made of polyphthalamide (PPA)or of carbon-fiber-reinforced PPA. The piston is preferably made of PPA(Grivory) reinforced with glass fibers and minerals. Typical dimensionsof the cylinder 4 are about 75 mm for the diameter and about 58 mm forthe length.

The cylinder 4, 4′ has a wall 40, a hollow space or pump chamber 41, aninlet/outlet 46 in the cylinder bottom 45, 45′, and an inlet/outlet 47in a cylinder head 49 lying opposite the cylinder bottom 45, 45′. Sincethe device is a double-action piston pump device, the inlets/outlets 46,47 act as inlet or outlet depending on the direction of movement of thepiston rod. The inlets/outlets 46, 47 are connected in a manner knownper se to a downstream valve block (not shown).

As can be seen from FIGS. 1 and 2, the pump cylinders 4, 4′ are securedon the support unit 2. For this purpose, the support unit 2 has asupport arm 20, which extends transverse to the longitudinal directionof the support unit 2 and protrudes on both sides of the main body ofthe support. The support unit 2, with the support arm, and the motorhousing are preferably made of metal or plastic.

The pump cylinders 4, 4′ are each anchored on the support arm 20 via arespective securing unit 3, 3′. This anchoring is preferably effectedvia a cylinder bottom 45, 45′. The cylinder bottom 45, 45′ is astationary component of the pump cylinder 4, 4′. The piston 42 movesrelative to the cylinder bottom 45, 45′. The cylinder bottom 45, 45′ ispreferably connected in a releasable manner to the rest of the cylinderby a screw connection. The corresponding screw holes are indicated byreference number 450 in FIGS. 4 and 5. The cylinder bottom 45, 45′ ispreferably recessed, in particular injection molded, and has a recess451 (FIG. 5) and an elevated circumferential edge.

According to the invention, the securing unit 3, 3′ comprises a leafspring clamp with at least one, preferably exactly one, leaf spring 36.There are preferably no other bearings, in particular no slidingbearings, ball bearings or roller bearings, present between the cylinderand the support unit.

As can be seen from FIG. 3, the securing unit 3, 3′ has a cylinder-sideclamping device and a support-side clamping device. Both devices consistin each case of a first and a second securing element 30, 32; 34, 33.The leaf spring 36 is clamped between the respective first securingelement 30, 34 and the associated second securing element 32, 33. Forthis purpose, screws 35, 37 are preferably present which extend throughthe first securing element 30, 34, the securing holes 360 of the leafspring 36, and the second securing element 32, 33. Corresponding holesare provided for this purpose in the first securing elements 30, 34 andin the second securing elements 32, 33. Some of these holes can be seenin FIGS. 4 and 5.

The cylinder-side first securing element 30 is preferably anchoredfixedly in the cylinder bottom 45. For this purpose, the cylinder bottom45 preferably has a securing seat 48 protruding from the rest of thebottom. The seat 48 is preferably produced in one piece with the rest ofthe cylinder bottom, for example by injection molding. The seat 48protrudes from the cylinder 4 at the end remote from the piston 42. Theseat 48 is reinforced on one side, for example by a base that widenstoward the cylinder bottom. This reinforcement is indicated by referencenumber 480 in FIGS. 4 to 6.

The seat 48 has a groove in which the cylinder-side first securingelement 30 is secured. The securing element 30 is preferably cast intoor welded into the seat or connected fixedly thereto in another way. Thesecuring element 30 is therefore preferably connected at least with aform-fit and material fit to the cylinder, more precisely the cylinderbottom.

As can be seen from FIGS. 3 to 6, the leaf spring 36 is screwed with itscylinder-side end, together with the cylinder-side second securingelement 32, onto the cylinder-side first securing element 30. The samehappens with the second support-side end of the leaf spring 36. Thesupport-side first securing element 34 and the associated secondsecuring element 33 can be seen in FIG. 3. The support-side firstsecuring element 34 is secured on the support arm 20 in a similar way orin the same way as its counterpart is secured on the cylinder bottom 45.Here too, the support arm 20 is preferably provided with a reinforcedseat for a form-fit and material fit connection to the support-sidefirst securing element 34. The seat can also be produced in one piecewith the support arm 20 or can at least be welded to the latter.

The embodiment according to FIG. 3, on the one hand, and the embodimentsaccording to FIGS. 4 to 6, on the other hand, differ particularly interms of the design of the cylinder bottom 45, particularly the inlet46, and the shape of the seat 48. Other shapes are possible.

Preferably, at least the cylinder-side first securing element 30 is madeof metal. It is preferably block-shaped or cuboid. The support-sidefirst securing element 34 is preferably also made in this shape and frommetal. In a preferred embodiment, the second securing elements 32, 33are also designed in this way.

The leaf spring 36 is short. The free length of the leaf spring 36between the clamps is preferably less than the width. Preferably, thelength is at least not substantially greater than the width. Typicalmeasurements for free length, width and thickness are circa 13 mm, 25 mmand 0.5 mm.

As can be seen from FIGS. 3 and 6, the leaf spring 36 extendssubstantially in a plane in which the longitudinal center axis of thecylinder 4 also extends. During operation, the cylinder 4, 4′, by virtueof the leaf spring 36, is now able to execute a pivoting movementrelative to the direction of movement of the piston 42. This appliesequally to both cylinders 4, 4′, since the securing device of the secondcylinder 4′ is identical to that of the first cylinder 4.

This arrangement can also be provided in other piston pumps. However,the suction pump shown here has further advantageous features which canalso be used independently of the above-described securing deviceaccording to the invention. The motor 1 can be actuated via anadjustment and control unit (not shown here). The adjustment and controlunit has in particular at least one adjustment possibility, preferablythree discrete adjustment possibilities, for the operation of the motor.These are, for example, three buttons, or a switch with three operatingpositions. For reasons of hygiene, capacitive sensors, particularly withthree operating positions, can also be used for this purpose. The switchcan also have an off position. These three operating positions eachselect a discrete motor speed and, therefore, three discrete suctioncapacities of the pump, for example 40 l/min, 50 l/min and 60 l/min. Themean suction capacity preferably corresponds to a normal operating stateor a recommended operating state. It is in this way possible to simplifythe operation of the pump, even when a motor is used which in principleis steplessly adjustable.

The piston pump device according to the invention is wear-resistant andruns quietly. When used as a suction pump, it additionally permits acontrollable air flow until the pump comes to a stop.

The invention claimed is:
 1. A piston pump device with a support unit, apump cylinder, and a pump piston arranged in the pump cylinder, the pumpcylinder having a longitudinal center axis, and a cylinder bottomarranged perpendicular to the longitudinal center axis, the pump pistonbeing movable relative to the cylinder bottom, and the pump cylinderbeing secured on the support unit by a securing unit, wherein thesecuring unit has a leaf spring, which permits a pivoting movement ofthe longitudinal center axis of the pump cylinder relative to thesupport unit, wherein the securing unit has a cylinder-side clampingdevice and a support-side clamping device, wherein the leaf spring has afirst end and a second end, and wherein the first end is clamped in thecylinder-side clamping device and the second end is clamped in thesupport-side clamping device.
 2. The piston pump device as claimed inclaim 1, wherein the securing unit is secured on the cylinder bottom. 3.The piston pump device as claimed in claim 1, wherein the securing unitforms a leaf spring clamp, and wherein the leaf spring clamp anchors thepump cylinder in relation to the support unit.
 4. The piston pump deviceas claimed in claim 1, wherein the leaf spring in the undeflected stateforms a plane, and wherein a rectilinear continuation of saidlongitudinal center axis runs in the plane.
 5. The piston pump device asclaimed in claim 1, wherein the leaf spring has a free length and awidth, wherein the leaf spring is made flexible in its free length, andwherein the ratio of free length to width is less than
 1. 6. The pistonpump device as claimed in claim 1, wherein the securing unit has asingle leaf spring.
 7. The piston pump device as claimed in claim 1,further comprising a cylinder-side first securing element formed in onepiece with the pump cylinder or welded onto the pump cylinder, or casttherein.
 8. The piston pump device as claimed in claim 7, wherein thecylinder-side first securing element is arranged in the cylinder bottom.9. The piston pump device as claimed in claim 8, wherein the cylinderbottom has a substantially plane area for closing the pump cylinder, andan outwardly protruding securing seat which is formed integrally on theplane area and which serves to receive the cylinder-side first securingelement.
 10. The piston pump device as claimed in claim 7, wherein thecylinder-side first securing element is a block-shaped metal piece. 11.The piston pump device as claimed in claim 1, wherein the cylinder-sideclamping device and the support-side clamping device each have a firstand a second securing element, wherein the leaf spring is clamped at thefirst end and the second end, two ends between the securing elements,and wherein a first and a second of the securing elements are in eachcase screwed together.
 12. The piston pump device as claimed in claim 1,further comprising two pairs consisting of a pump cylinder, a piston anda securing unit, and wherein the longitudinal center axes of the pumpcylinders extend parallel to each other in the undeflected state of thepump cylinders.
 13. A suction pump comprising: a piston pump devicehaving a support unit; a pump cylinder having a longitudinal center axisand a cylinder bottom arranged perpendicular to the longitudinal centeraxis; a pump piston arranged in the pump cylinder, the piston beingmoveable relative to the cylinder bottom; a securing unit for securingthe pump cylinder on the support unit; a crankshaft for moving the pumppiston; a motor for driving the crankshaft; and a gear mechanismconnecting the motor and the crankshaft, the gear mechanism being asing-stage gear; wherein the securing unit has a leaf spring whichpermits a pivoting movement of the longitudinal center axis of the pumpcylinder relative to the support unit, wherein the securing unit has acylinder-side clamping device and a support-side clamping device,wherein the lead spring has a first end and a second end, and whereinthe first end is clamped in the cylinder-side clamping device and thesecond end is clamped in the support-side clamping device.
 14. Thesuction pump as claimed in claim 13, wherein an adjustment and controlunit is present, by means of which the motor is adjustable to at leastone speed.
 15. The suction pump as claimed in claim 14 wherein the motoris adjustable to exactly three discrete speeds.
 16. A piston pump devicewith a support unit, a pump cylinder, and a pump piston arranged in thepump cylinder, the pump cylinder having a longitudinal center axis, anda cylinder bottom arranged perpendicular to the longitudinal centeraxis, the pump piston being movable relative to the cylinder bottom, andthe pump cylinder being secured on the support unit by a securing unit,wherein the securing unit has a leaf spring, which permits a pivotingmovement of the longitudinal center axis of the pump cylinder relativeto the support unit, the piston pump device further comprising acylinder-side first securing element formed in one piece with the pumpcylinder or welded onto the pump cylinder, or cast therein, and whereinthe cylinder-side first securing element is a block-shaped metal piece.17. A piston pump device with a support unit, a pump cylinder, and apump piston arranged in the pump cylinder, the pump cylinder having alongitudinal center axis, and a cylinder bottom arranged perpendicularto the longitudinal center axis, the pump piston being movable relativeto the cylinder bottom, and the pump cylinder being secured on thesupport unit by a securing unit, wherein the securing unit has a leafspring, which permits a pivoting movement of the longitudinal centeraxis of the pump cylinder relative to the support unit, the piston pumpdevice further comprising two pairs consisting of a pump cylinder apiston and a securing unit, and wherein the longitudinal center axis ofthe pump cylinder extend parallel to each other in the undeflected stateof the pump cylinders.